1. Field of the Invention
The present invention relates to an image-recording process and an image-recording apparatus capable of giving curls of desired direction and size at desired position of various image-recording materials.
2. Description of the Related Art
A toner used for electrophotographic recording is melted and flattened so as to be hardened and fixed on a surface of an image-receiving sheet by heat and pressure fixing process. As a result, a thermoplastic resin is used as a binder of the toner. Also, an image-receiving layer which comprises the thermoplastic resin is disposed on a surface of a support for the image-receiving sheet with an object to increase the fixing property of the toner. The thermoplastic resin of a toner and image-receiving layer like this, normally, together with plastic deformability, has elastic deformability generally. The image-receiving sheet with which the toner is transferred on the image-receiving layer is heated and pressurized, melt deformed and flattened, and fixed on the surface of the image-receiving layer by a fixing process comprising heating and pressurizing roller. After that, when the fixing process is passed through and stress is released, on the toner and image-receiving layer, during the period until they are cooled, elastic recovered and the action of returning from the flattened state to the original is worked, as a result, contractive force is generated on the surface of the image-receiving layer and the image-receiving sheet curls so that the surface of the image-receiving layer becomes a concave shape. This especially is remarkable when the amount of the toner is plenty at high density image, and when the thickness of the receiving layer of high image quality use is thick.
The curl phenomenon is common not only in electrophotographic material, but also in recording method by heating in which the thermoplastic resin is used in a color material and an image-receiving layer. For example, in transfer material and sublimation-transfer materials provided with donor film and a receiving layer, and a heat-sensitive material, the same problem is occurred.
Also, image-receiving sheet is used a lot in roll-feed paper which is advantageous in high speediness and cost, as a result, the winding habit remains and the remaining curl also remains on the sheet after image fixing, especially, in the case of seeking high image quality and high durability like photographic print, as image-receiving layer comprising the thermoplastic resin is disposed, or a support coated or laminated with the thermoplastic resin on the raw paper is used, there is a problem that furthermore, the winding habit remains easily and the winding habit correction is difficult.
The curl problem caused by the winding habit in the above-mentioned rolled form is common and true in an image-recording material comprising a thermoplastic resin in a color material and an image-receiving layer, namely, an electrophotographic material, a heat-transfer material, a sublimation-transfer material, a heat-sensitive material comprising donor film and image-receiving layer, ink-jet material comprising ink image-receiving layer, and the like also has similar curl occurring problem.
As a method of suppressing the curl occurring because of various factors like this, for example, Japanese Patent Application Laid-Open (JP-A) No. 04-501925 and Japanese Patent Application Laid-Open (JP-A) No. 2004-4596 propose an improvement of the image-receiving sheet. However, as both proposals receive the influence of donor and fixing condition, there is a problem of little effect to the curl in the final image output sheet.
Also, a fixing apparatus comprising belt fixing step, is proposed in Japanese Patent Application Laid-Open (JP-A) No. 05-72926. According to this proposal, though there is a constant effect to increase glossiness and to prevent offset, the controlling of the direction and size of the curl is impossible, and when the image output speed becomes high speed, there is a problem that the curl correction becomes insufficient.
Moreover, not only merely suppressing the occurrence of the curl, like photographic print, there is a case also where the surface of an image prefers to become more or less a concave shape, it is also desired that the controlling of the direction and size of the curl satisfies the needs of the user.